Method For Manufacturing A Nanoparticle, Method For Manufacturing A Light-Emitting Element Having The Nanoparticle, And Method For Manufacturing A Display Substrate Having The Nanoparticle

ABSTRACT

In a method for manufacturing a nanoparticle, a precursor (e.g., transition metal complex) mixed with polyethylene glycol (PEG) is thermally decomposed. A nanoparticle is formed from the thermal decomposition. PEG is cost effective and less toxic than chemicals that are conventionally used for nanoparticle production, so that costs for manufacturing the nanoparticle may be decreased. Further, PEG may be reused to produce more nanoparticles.

PRIORITY STATEMENT

This application claims priority under 35 U.S.C §119 to Korean PatentApplication No. 2008-118717 filed on Nov. 27, 2008 in the KoreanIntellectual Property Office (KIPO), the contents of which are hereinincorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a method of manufacturing a nanoparticle, amethod of manufacturing a light-emitting element with the nanoparticle,and a method of manufacturing a display substrate using thenanoparticle. More particularly, the invention relates to a method ofmanufacturing a nanoparticle that emits light, a method formanufacturing a light-emitting element having the nanoparticle, and amethod for manufacturing a display substrate having the nanoparticle.

2. Description of the Related Art

Generally, in the field of nanotechnology, a material or a device ismade using nanosize particles (nanoparticles). “Nanoparticles,” as usedherein, are particles having size parameters (such as length, height,diameter, width, etc.) in a nanometer range, and nanotechnology mayinclude a method for manufacturing the material or the device as well asthe material or device itself. A “nanometer range” covers about 1 nm toabout 100 nm.

The nanoparticles may be zero-dimensional (0D), one-dimensional (1D),two-dimensional (2D), etc. A 0D nanoparticle may include a quantum dot,a 1D nanoparticle may include a nanowire, a nanopipe, etc., and a 2Dnanoparticle may include a nanodisc.

In nanotechnology, a quantum dot may have different kinds of optical,electrical and/or magnetic properties compared to the bulk material.Furthermore, a quantum dot's optical, electrical, and/or magneticproperties may change with the size or the shape of the quantum dot. Thequantum dot having the above-mentioned characteristics is used inmanufacturing a silicon semiconductor or a thin metal layer, etc., sothat technical limitations in manufacturing the silicon semiconductor orthe thin metal layer may be overcome.

The quantum dot is usually formed via a lithographic process or agas-liquid-solid phase growth process using a catalyst, using anexpensive apparatus. Today, quantum dots may be formed in a solution.For example, quantum dots may be formed using a solution that includesoctadecene, trioctylphosphine oxide, etc.

However, the above-mentioned solutions are relatively expensive,increasing the cost for manufacturing the quantum dot. In addition,octadecene and trioctylphosphine oxide are usually discarded after beingused, introducing pollutants to the environment.

SUMMARY OF THE INVENTION

The present invention provides a method for manufacturing a nanoparticlecapable of improving the productivity of the nanoparticle, a method formanufacturing a light-emitting element having the nanoparticle, and amethod for manufacturing a display substrate having the nanoparticle.

According to one aspect of the present invention, a method formanufacturing a nanoparticle is provided. The method includes mixing aprecursor with polyethylene glycol (PEG) to form a first mixture, andthermally decomposing the first mixture.

The PEG may have a weight average molecular weight in a range of about1,500 to about 4,000.

In thermally decomposing the precursor, the first mixture may beagitated at a temperature in a range of about 100° C. to about 300° C.

After forming the nanoparticle, the PEG in which the nanoparticle isformed may be mixed with a hydrophobic solution having a higherhydrophobicity than PEG. Solid-state PEG may be separated from thenanoparticle by precipitation.

PEG mixed with the precursor may be collected via transforming a phaseof solid-state PEG.

The hydrophobic solution may include hexane, chloroform, cyclohexane,etc.

A second transition metal complex may be mixed with the first mixture.The second transition metal complex may be thermally decomposed in PEGto form an outer layer on a surface of the nanoparticle, the outer layerincluding a second transition metal of the second transition metalcomplex.

The nanoparticle may include transition metal oxide, transition metalsulfide, transition metal selenide, transition metal telluride,transition metal nitride, transition metal phosphide, transition metalarsenide, etc.

According to one aspect of the present invention, a method formanufacturing a light-emitting element is provided. The method includesmixing a precursor mixed with PEG to form a first mixture and thermallydecomposing the first mixture to form a nanoparticle. A first electrodelayer may be formed on a substrate. A light-emitting layer may be formedon the substrate including the first electrode, the light-emitting layerhaving the nanoparticle. A second electrode layer may be formed on thelight-emitting layer.

According to one aspect of the present invention, a method formanufacturing a display substrate is provided. In method, a precursormixed with PEG may be thermally decomposed to form a nanoparticle. Acolor layer may be formed in a pixel area of a substrate, the colorlayer having the nanoparticle.

According to the present invention, a nanoparticle may be formed usingPEG as a solvent. PEG is cheap and less toxic, and PEG used in formingthe nanoparticle may be recycled. Thus, costs for manufacturing thenanoparticle may be decreased and the productivity of the nanoparticlemay be improved.

In addition, the nanoparticle formed in PEG may be used in a method formanufacturing a light-emitting element and a display substrate, and thusthe productivity of the light-emitting element and the display substratemay be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present inventionwill become more apparent by describing in detailed embodiments thereofwith reference to the accompanying drawings.

FIG. 1 is a flowchart illustrating a method for manufacturing ananoparticle according to an embodiment of the present invention;

FIGS. 2A and 2B are graphs illustrating characteristics of thenanoparticles produced according to Example 1;

FIGS. 3A and 3B are images showing the nanoparticles produced accordingto Example 2;

FIGS. 4A and 4B are graphs illustrating characteristics of thenanoparticles produced according to Example 2;

FIG. 5 is a cross-sectional view illustrating a light-emitting elementaccording to another embodiment of the present invention;

FIG. 6 is a cross-sectional view illustrating a light source includingthe light-emitting element of FIG. 5;

FIG. 7 is a circuit diagram illustrating a display substrate in a methodfor manufacturing the display substrate according to still anotherembodiment of the present invention;

FIG. 8 is a cross-sectional view illustrating the display substrate inFIG. 7;

FIG. 9 is a plan view illustrating the display substrate in FIG. 7; and

FIG. 10 is a cross-sectional view illustrating the method formanufacturing the display substrate shown in FIG. 9.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is described more fully hereinafter with referenceto the accompanying drawings, in which exemplary embodiments of thepresent invention are shown. The present invention may, however, beembodied in many different forms and should not be construed as limitedto the exemplary embodiments set forth herein. These embodiments areprovided to complete the disclosure and convey the scope of theinvention to those skilled in the art. In the drawings, the sizes andrelative sizes of layers and regions may be exaggerated for clarity.

It will be understood that when an element or layer is referred to asbeing “on,” “connected to” or “coupled to” another element or layer, itcan be directly on, connected or coupled to the other element or layeror intervening elements or layers may be present. In contrast, when anelement is referred to as being “directly on,” “directly connected to”or “directly coupled to” another element or layer, there are nointervening elements or layers present. Like numerals refer to likeelements throughout. As used herein, the term “and/or” includes any andall combinations of one or more of the associated listed items.

It will be understood that, although the terms first, second, third,etc. may be used herein to describe various elements, components,regions, layers and/or sections, these elements, components, regions,layers and/or sections should not be limited by these terms. These termsare only used to distinguish one element, component, region, layer orsection from another region, layer or section. Thus, a first element,component, region, layer or section discussed below could be termed asecond element, component, region, layer or section without departingfrom the teachings of the present invention.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the exemplary term “below” can encompass both anorientation of above and below. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particularan embodiment only and is not intended to be limiting of the presentinvention. As used herein, the singular forms “a,” “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises” and/or “comprising,” when used in this specification,specify the presence of stated features, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,elements, components, and/or groups thereof.

Embodiments of the invention are described herein with reference tocross-sectional illustrations that are schematic illustrations ofidealized embodiments (and intermediate structures) of the presentinvention. As such, variations from the shapes of the illustrations as aresult, for example, of manufacturing techniques and/or tolerances, areto be expected. Thus, example embodiments of the present inventionshould not be construed as limited to the particular shapes of regionsillustrated herein but are to include deviations in shapes that result,for example, from manufacturing. For example, an implanted regionillustrated as a rectangle will, typically, have rounded or curvedfeatures and/or a gradient of implant concentration at its edges ratherthan a binary change from implanted to non-implanted region. Likewise, aburied region formed by implantation may result in some implantation inthe region between the buried region and the surface through which theimplantation takes place. Thus, the regions illustrated in the figuresare schematic in nature and their shapes are not intended to illustratethe actual shape of a region of a device and are not intended to limitthe scope of the present invention.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

FIG. 1 is a flowchart illustrating a method for manufacturing ananoparticle according to an embodiment of the present invention.

Referring to FIG. 1, a precursor for forming a nanoparticle is mixedwith polyethylene glycol (PEG) (step S10) to form a first mixture.

PEG may be a compound including a chain and a couple of alcoholfunctionalities (—OH) coupled to respective ends of the chain. The chainmay include ethylene oxide (—CH₂CH₂O—) as a repeating unit. When theweight average molecular weight of PEG is less than about 1,500, PEG maynot have native physical and/or chemical characteristics of thecompound. When the weight average molecular weight of PEG is greaterthan about 4,000, the melting point of PEG may be increased and theprecursor becomes difficult to mix with PEG. Thus, the weight averagemolecular weight of PEG may be in a range between about 1,500 to about4,000.

The precursor may include a transition metal complex. The transitionmetal complex may include a transition metal which forms thenanoparticle. Examples of suitable transition metals include gold (Au),silver (Ag), platinum (Pt), palladium (Pd), cobalt (Co), copper (Cu),molybdenum (Mo), zinc (Zn), cadmium (Cd), mercury (Hg), gallium (Ga),indium (In), tin (Sn), lead (Pb), etc. These substances may be usedalone or in a mixture. Examples of a material that may be used for thetransition metal complex include indium acetate, diethyl zinc, cadmiumacetate, etc.

The transition metal complex may be mixed with PEG after being dissolvedin a first solvent to facilitate the transition metal complex's mixingwith PEG The solution formed using the first solvent and the transitionmetal complex may be mixed with PEG. Examples of a material that may beused for the first solvent may include myristic acid, oleic acid, oleylamine, etc.

An organic compound may be further mixed with PEG after mixing theprecursor with PEG. Examples of a material that may be used for theorganic compound may include oxide, sulfide, selenide, telluride,nitride, phosphide, arsenide, etc. Particular examples of a materialthat may be used for the organic compound may includetris(trimethylsilyl)phosphine, bis(trimethylsilyl)sulfide, etc.

In addition, the organic compound may be mixed with PEG after beingdissolved in a second solvent in order to be easily mixed with PEG Theorganic compound and the second solvent may be mixed with PEG Examplesof a material that may be used for the second solvent may includetrioctylphosphine (TOP), etc.

The precursor which is mixed with PEG may be thermally decomposed (stepS20).

The precursor mixed with PEG of the first mixture may be agitated atabout 100° C. to about 300° C. to be thermally decomposed. Where one ormore organic compound was added, the organic compound mixed with theprecursor and PEG is agitated.

When an agitating temperature is less than about 100° C., the providedenergy level may not be sufficient for decomposition of the precursor,possibly resulting in complete decomposition of the precursor. On theother hand, when the agitating temperature is greater than about 300°C., PEG may decompose or non-essential reactions may be generated due toexcessive heat, decreasing the reliability in the thermal decompositionof the precursor. Thus, the temperature for the thermal decomposition ofthe precursor is preferably in a range between about 100° C. to about300° C.

The transition metal which is formed from the precursor mayindependently exist in PEG, via thermal decomposition of the precursor.

The nanoparticle is formed via thermally decomposing the precursor inPEG (step S30).

For example, the transition metal which is formed from the precursor mayform the nanoparticle. The nanoparticle may include gold (Au), silver(Ag), platinum (Pt), palladium (Pd), cobalt (Co), copper (Cu),molybdenum (Mo), indium phosphide (InP), cadmium selenide (CdSe), copperindium selenide (CuInSe₂), copper indium sulfide (CuInS₂), gold indiumsulfide (AgInS₂), etc.

Although not shown in figures, after forming the nanoparticle, an outerlayer of the nanoparticle may be formed on a surface of thenanoparticle. In this case, the outer layer may be formed by adding atransition metal complex including a different transition metal and thetransition metal of the nanoparticle to PEG which is mixed with thenanoparticle, as a second mixture. Thus, the nanoparticle having acore-shell structure may be formed by the first mixture and the secondmixture. Hereinafter, the transition metal of the nanoparticle isreferred to as “a first transition metal” and the different transitionmetal of the outer layer is referred to as “a second transition metal.”For example, the nanoparticle may be formed from the transition metalcomplex as the precursor which includes the first transition metal. Thenanoparticle may be defined as the “core” of the core-shell structure.The outer layer may include the second transition metal and be definedas the “shell” of the core-shell structure.

For example, a second transition metal complex having the secondtransition metal may be mixed with PEG which is mixed with thenanoparticle. The second transition metal may be different from thefirst transition metal. Examples of the second transition metal includegold (Au), silver (Ag), platinum (Pt), palladium (Pd), cobalt (Co),copper (Cu), molybdenum (Mo), zinc (Zn), cadmium (Cd), mercury (Hg),gallium (Ga), indium (In), tin (Sn), lead (Pb), etc. These may be usedalone or in a mixture.

Then, the second transition metal complex may be thermally decomposed inPEG which is mixed with the nanoparticle to form a thermally decomposedmaterial. The thermally decomposed material may form the outer layerincluding the second transition metal. The outer layer may be formed ona surface of the nanoparticle. A process for thermally decomposing thesecond transition metal complex is substantially the same as that forthermally decomposing the first transition metal complex. Thus, anyfurther repetitive description concerning the above process will beomitted.

In addition to the second transition metal complex, an organic compoundmay be further added to PEG mixed with the nanoparticle. The organiccompound added to PEG with the second transition metal complex issubstantially the same as or similar to the organic compound added toPEG with the first transition metal complex. Thus, any furtherrepetitive description concerning the above element will be omitted.

Hereinafter, the “nanoparticle” is defined to include a nanoparticlehaving the first transition metal and having a core and an outer layer.In this case, the core includes the first transition metal, and theouter layer includes the second transition metal and surrounds the core.

PEG and the nanoparticle are mixed with a hydrophobic solvent (stepS40).

The hydrophobic solvent may include a material having a higherhydrophobicity than PEG. Examples of a material that may be used for thehydrophobic solvent include hexane, chloroform, cyclohexane, etc. In thehydrophobic solvent and PEG the hydrophobic solvent may have hydrophobiccharacteristics and PEG may have hydrophilic characteristics compared tothe hydrophobic solvent. The hydrophobic solvent may have the higherhydrophobicity than PEG, and thus PEG may not dissolve in thehydrophobic solvent. Thus, PEG precipitates out of the hydrophobicsolvent to form solid-state PEG.

Before mixing PEG and the nanoparticle with the hydrophobic solvent, PEGand the nanoparticle may be cooled to a temperature that is lower thanthat for thermal decomposition. PEG and the nanoparticle may be cooledat a temperature between about 50° C. to about 70° C.

The size of the nanoparticle may be controlled by controlling the timeperiod between thermal decomposition process and the process for mixingPEG with the hydrophobic solvent. Specifically, the longer this timeperiod is, the larger the size of the nanoparticle will be. The size ofthe nanoparticle may depend on the size of the core and/or thickness ofthe outer layer. For example, the larger the size of the core is and/orthe thicker the outer layer, the larger the overall size of thenanoparticle will be.

Then, solid-state PEG which is precipitated in the hydrophobic solventis separated from the nanoparticle (step S50).

The solid-state PEG may be phase-separated from the hydrophobic solvent.For example, the solid-state PEG may remain in a first container afterpouring the hydrophobic solvent into a second container different fromthe first container. The nanoparticle may be dissolved in thehydrophobic solvent, and thus the nanoparticle may be moved into thesecond container with the hydrophobic solvent when pouring thehydrophobic solvent into the second container.

Solid-state PEG is collected after phase-transforming solid-state PEGwhich is separated from the nanoparticle and the hydrophobic solvent(step S60).

In more detail, solid-state PEG may be heated to transform solid-statePEG into liquid-state PEG. The liquid-state PEG may be substantially thesame as PEG used in the initial step for manufacturing the nanoparticle.Thus, the liquid-state PEG may be reused for manufacturing thenanoparticle. For example, the precursor of the nanoparticle may bemixed with the liquid-state PEG to be used again in manufacturing morenanoparticles.

The nanoparticle dissolved in the hydrophobic solvent may be separatedfrom the hydrophobic solvent by removing the hydrophobic solvent fromthe second container. For example, the hydrophobic solvent may beremoved from the second container by vaporizing the hydrophobic solvent.

In addition, after separating the nanoparticles from the hydrophobicsolvent, the nanoparticles may be centrifuged to be divided according tosize.

According to the method for manufacturing the nanoparticle in thepresent embodiment, the nanoparticle may be formed using PEG as asolvent which is cheap and less toxic. An added benefit of the methoddescribed above is that PEG used in forming the nanoparticle may berecycled or reused. Thus, manufacturing cost may be decreased and theproductivity of the nanoparticle may be improved.

Hereinafter, the method for manufacturing the nanoparticle will beillustrated through the following embodiments.

EXAMPLE 1 Manufacturing Cadmium Selenide (CdSe)

After mixing about 0.2 mmol of cadmium acetate with 1 mL of oleic acidto form a mixing solution, the mixing solution was agitated in a vacuumcondition at a temperature of about 100° C., for about 1 hour. About 1mL of trioctylphosphine (TOP) and a shot of 0.8 mmol selenium were mixedwith an agitated mixing solution to form a precursor of CdSe.

Then, after heating about 4 g of PEG (the weight average molecularweight of which about 3,350) and 1 mL of oleyl amine in a nitrogen gascondition and a temperature of about 200° C. for about 1 minute to about1 hour, the precursor of CdSe was added in the above solution includingPEG and oleyl amine to manufacture CdSe having an average diameter ofabout 4 nm.

Obtained products were cooled at a temperature of about 60° C., andhexane was added to the obtained products to separate solid-state PEG byprecipitation.

FIGS. 2A and 2B are graphs illustrating characteristics of thenanoparticles according to Example 1.

FIG. 2A represents light absorption of CdSe in PEG as a function ofwavelength when reaction time is about 1 minute, about 2 minutes, about3 minutes, about 4 minutes, about 5 minutes, about 6 minutes, and about7 minutes. In FIG. 2A, the x-axis represents the wavelength (nanometers,nm). The y-axis represents relative light absorption which has a maximumvalue “1” and a minimum value “0”. The reaction time indicates a periodin which the precursor of CdSe reacts in PEG after the precursor isadded to PEG.

Referring to FIG. 2A, the wavelength at which light absorption is atabout 0 increases as the reaction time passes from about 1 minute toabout 5 minutes. When the reaction time is about 1 minute, the lightabsorption is about 0 at the wavelength of about 580 nm. When thereaction time is about 2 minutes, the light absorption is about 0 at thewavelength of about 600 nm. When the reaction time is about 5 minutes,the light absorption is about 0 at the wavelength of about 630 nm.

FIG. 2B represents light (photoluminescence) intensity of CdSe in PEGaccording to the wavelength when the reaction time is about 1 minute,about 2 minutes, about 3 minutes, about 4 minutes, about 5 minutes,about 6 minutes, and about 7 minutes. In FIG. 2B, the x-axis representsthe wavelength (nanometers, nm). The y-axis represents relativeintensity of emitted light which has a maximum value “1” and a minimumvalue “0”.

Referring to FIG. 2B, the wavelength at which the light intensity isabout 1 increases as the reaction time increases from about 1 minute toabout 5 minutes. When the reaction time is about 1 minute, the lightintensity is about 1 at the wavelength of about 500 nm. When thereaction time is about 2 minutes, the light intensity is about 1 at thewavelength of about 540 nm. When the reaction time is about 3 minutes,the light intensity is about 1 at the wavelength of about 580 nm. Whenthe reaction time is about 5 minutes, the light intensity has about 1 atthe wavelength of about 600 nm.

Referring to FIGS. 2A and 2B, a nanoparticle formed in PEG absorbs andemits light of longer wavelength as the reaction progresses. The size ofthe nanoparticle may grow large, as the reaction time passes. Thenanoparticle may represent a blue color corresponding to the shortwavelength to a red color corresponding to the long wavelength, as thesize of the nanoparticle is increased.

EXAMPLE 2 Manufacturing Indium Phosphide/Zinc Sulfide (InP/ZnS)

After preparing a mixing solution including indium acetate of about 0.4mmol and myristic acid of about 1.7 mmol with PEG (the weight averagemolecular weight of about 3,350) of about 4 g, the mixing solution andPEG were agitated in a nitrogen condition which had a temperature ofabout 120° C., for about 1 hour. The agitated product was mixed withtris(trimethylsilyl)phosphine of about 0.2 mmol dispersed in TOP ofabout 0.5 ml at a temperature of about 180° C. to form a precursor ofindium phosphide (InP). The precursor of InP was heated at a temperatureof about 180° C. for about 3 minutes, and thus InP having the diameterof about 3.7 was formed.

Then, after a mixture including 0.3 mmol of diethyl zinc dispersed in 1mL TOP and about 0.3 mmol bis-(trimethylsilyl)sulfide were dropped inthe above products which included InP and PEG at a temperature of about120° C., the above products including the mixture, InP and PEG wereagitated and heated at a temperature of about 200° C., for about 1 hour.Thus, InP/ZnS including ZnS was formed. ZnS surrounded InP as andInP/ZnS had the diameter of about 5.1 nm.

The above products including InP/ZnS and PEG were cooled at atemperature of about 60° C., and hexane was added to the obtainedproducts to separate solid-state by precipitation.

FIGS. 3A and 3B are images showing the nanoparticles prepared accordingto Example 2.

For example, FIG. 3A is an image of InP formed in PEG, and the image wastaken by a transmitting electron microscope. FIG. 3A shows that InPhaving a diameter of about 3.7 nm may be formed in PEG.

FIG. 3B is an image of InP/ZnS formed in PEG, and the image was taken bythe transmitting electron microscope. In FIG. 3B, InP/ZnS having thediameter of about 5.1 nm may be formed in PEG.

FIGS. 4A and 4B are graphs illustrating characteristics of thenanoparticles according to Example 2.

FIG. 4A represents a light absorption of InP/ZnS in PEG according to thewavelength, when a reaction time is about 1 minute, about 2 minutes,about 3 minutes, about 4 minutes, about 5 minutes, about 6 minutes, andabout 7 minutes. In FIG. 4A, the x-axis represents the wavelength(nanometers, nm). The y-axis represents relative light absorption whichhas a maximum value “1” and a minimum value “0”. The reaction timeindicates the period in which the precursor of ZnS reacts in PEG and InPafter the precursor is added to PEG and InP.

Referring to 4A, the wavelength having the light absorption of about 0may be increased, as the reaction time passes from about 1 minute toabout 7 minutes. When the reaction time is about 1 minute, the lightabsorption is about 0 at the wavelength of about 600 nm. When thereaction time is about 2 minutes, the light absorption is about 0 at thewavelength of about 620 nm. When the reaction time is about 7 minutes,the light absorption is about 0 at the wavelength of about 800 nm.

FIG. 4B represents the intensity of light emitted from InP/ZnS in PEGaccording to the wavelength when the reaction time is at about 1 minute,about 2 minutes, about 3 minutes, about 4 minutes, about 5 minutes,about 6 minutes, and about 7 minutes. In FIG. 2B, the x-axis representsthe wavelength (nanometers, nm). The y-axis represents relative lightintensity which has a maximum value “1” and a minimum value “0”.

Referring to FIG. 4B, wavelength having the light intensity of about 1may increase as the reaction time increases from about 1 minute to about5 minutes. When the reaction time is about 1 minute, the light intensityis about 1 at the wavelength of about 500 nm. When the reaction time isabout 2 minutes, the light intensity is about 1 at the wavelength ofabout 530 nm. When the reaction time is about 3 minutes, the lightintensity is about 1 at the wavelength of about 560 nm. When thereaction time is about 4 minutes, the light intensity is about 1 at thewavelength of about 600 nm. When the reaction time is about 5 minutes,the light intensity is about 1 at the wavelength of about 630 nm. Whenthe reaction time is about 6 minutes, the light intensity is about 1 atthe wavelength of about 660 nm. When the reaction time is about 7minutes, the light intensity is about 1 at the wavelength of about 680nm.

In FIGS. 4A and 4B, the nanoparticle formed in PEG absorbs and emitslight of increasing wavelength as the reaction time increases. The sizeof the nanoparticle may grow large, as the reaction time passes. Thenanoparticle may represent a blue color corresponding to the shortwavelength to a red color corresponding to the long wavelength, as thesize of the nanoparticle is increased.

Hereinafter, a method for manufacturing a light-emitting element will beexplained referring to FIGS. 5 to 8.

FIG. 5 is a cross-sectional view illustrating a light-emitting elementin a method for manufacturing the light-emitting element according toanother embodiment of the present invention.

First, the light-emitting element will be briefly explained as follows.Referring to FIG. 5, the light-emitting element 500 may include a firstelectrode layer 20 formed on a substrate 10, a light-emitting layer 30formed on the first electrode layer 20, and a second electrode layer 40formed on the light-emitting layer 30.

The first electrode layer 20 may provide a hole for the light-emittinglayer 30. The second electrode layer 40 may provide an electron for thelight-emitting layer 30.

A hole and an electron combine in the light-emitting layer 30 to emitlight. The light-emitting layer 30 may include a plurality ofnanoparticles. Examples of a material that may be used for thenanoparticle may include gold (Au), silver (Ag), platinum (Pt),palladium (Pd), cobalt (Co), copper (Cu), molybdenum (Mo), indiumphosphide (InP), cadmium selenide (CdSe), copper indium selenide(CuInSe₂), copper indium sulfide (CuInS₂), gold indium sulfide (AgInS₂),indium phosphide/zinc sulfide (InP/ZnS), etc.

Although not shown in the figures, the light-emitting element 50 mayfurther include a hole injection layer and/or a hole transferring layerwhich are disposed between the first electrode layer 20 and thelight-emitting layer 30. In addition, the light-emitting layer 50 mayfurther include an electron injection layer and/or an electrontransferring layer which are disposed between the second electrode layer40 and the light-emitting layer 30.

Referring to FIG. 5, the method for manufacturing the light-emittingelement will be explained as follows. First, the nanoparticles areformed using PEG A method for forming the nanoparticle according to thepresent embodiment is substantially the same as the method according tothe previous embodiment in FIG. 1. Thus, any further repetitivedescription will be omitted.

The nanoparticle may be coated on the substrate 10 including the firstelectrode layer 20 to form the light-emitting layer 30. For example, asolution including the nanoparticle may be dropped on the substrate 10including the first electrode layer 20 and a solvent of the solution maybe evaporated from the substrate 10. Then, the nanoparticle may remainon the substrate 10 to form the light-emitting layer 30. Then, thesecond electrode layer 40 is formed on the substrate 10 including thelight-emitting layer 30 to manufacture the light-emitting element 50according to the present embodiment.

FIG. 6 is a cross-sectional view illustrating a light source includingthe light-emitting element 50 of FIG. 5.

Referring to FIG. 6, the light-emitting element 50 according to thepresent example embodiment may be used in a light source 100. The lightsource 100 may include a light-emitting element 50 as explained in FIG.5, a first electrode line 60, a second electrode line 70, a wire 80, andlens 90.

The light-emitting element 50 according to the present embodiment issubstantially the same as the light-emitting element according to theembodiment in FIG. 5. The first electrode line 60 may be electricallyconnected to the first electrode layer 20 of the light-emitting element50. The second electrode line 70 may face the first electrode line 60and be electrically connected to the second electrode layer 40 of thelight-emitting element 50 through the wire 80. The lens 90 may cover thelight-emitting element 50, the first electrode line 60, the secondelectrode line 70, and the wire 80, and diffuse the light emitted fromthe light-emitting element 50.

The light source 100 including the light-emitting element 50 ismanufactured using a nanoparticle which is formed in PEG In a method formanufacturing the light source 100, a method for forming thelight-emitting element 50 according to the present embodiment issubstantially the same as the light-emitting element according to theprevious example embodiment in FIG. 5. The light-emitting element 50 maybe combined with the first electrode line 60, the second electrode line70, the wire 80, and the lens 50 to manufacture the light source 100.

FIG. 7 is a circuit diagram illustrating a display substrate in a methodfor manufacturing the display substrate according to still anotherexample embodiment of the present invention.

Referring to FIG. 7, a display substrate 200 may include a gate line GL,a data line DL, a power supply line VL, a switching transistor Qs, adriving transistor Qd, and a light-emitting element 50. Each pixel areaPx of the display substrate 200 may include the switching transistor Qs,the driving transistor Qd, the light-emitting element 50, and a storagecapacitor Cst.

The gate line may extend in a first direction of the display substrate200. The data line DL may extend in a second direction different fromthe first direction and cross the gate line GL. The gate line GL and thedata line DL may be connected to the switching transistor Qs. The powersupply line VL may extend in the first direction and be disposedparallel with the gate line GL. The power supply line VL may beconnected to the driving transistor Qd. The driving transistor may beconnected to the switching transistor Qs.

The switching transistor Qs may include a first gate electrode GE1connected to the gate line GL, a first source electrode SE1 connected tothe data line DL1, and a first drain electrode DE1 spaced apart from thefirst source electrode SE1.

The driving transistor Qd may include a second gate electrode GE2connected to the first drain electrode DE1, a second source electrodeSE2 connected to the power supply line VL, and a second drain electrodeDE2 spaced apart from the second source electrode SE2.

The light-emitting element 50 may include a first electrode layer, alight-emitting layer, and a second electrode layer. The light-emittingelement 50 according to the present embodiment is substantially the sameas the light-emitting element according to the embodiment in FIG. 5.

FIG. 8 is a cross-sectional view illustrating the display substrate inFIG. 7.

Referring to FIG. 8, a method for manufacturing of a display substrateincluding a light-emitting element will be explained. The first andsecond gate electrodes GE1 and GE2 may be formed on a base substrate210. A first insulating layer 220 may be formed on the base substrate210 including the first and second electrodes GE1 and GE2. An activepattern AP of the driving transistor Qd may be formed on the basesubstrate 210 including the first insulating layer 220. The first andsecond source electrodes SE1 and SE2 and the first and second drainelectrodes DE1 and DE2 may be formed on the base substrate 210 includingthe active pattern AP. A second insulating layer 230 and a thirdinsulating layer 240 may be formed on the base substrate 210 includingthe first and second source electrodes SE1 and SE2 and the first andsecond drain electrodes DE1 and DE2. The first electrode layer 20 may beformed on the third insulating layer 240. In forming the first electrodelayer 20, the first drain electrode DE1 may be electrically connected tothe second gate electrode GE2.

Then, an insulating wall WA may be formed in a region of the displaysubstrate 200 except for the pixel area Px, and is formed on the basesubstrate 210 on which the first electrode layer 20 is formed. Forexample, the insulating wall WA may be formed in the region in which thegate line GL and the data line DL are formed.

A light-emitting layer 30 may be formed on the base substrate 210including the insulating wall WA via coating a nanoparticle. Forming thelight-emitting layer 30 according to the present embodiment issubstantially the same as the process described above for the embodimentin FIG. 5. Thus, any further repetitive description will be omitted.

A second electrode layer 40 may be formed on the base substrate 210including the light-emitting layer 50 to manufacture the displaysubstrate 200 including the light-emitting element 50.

FIG. 9 is a plan view illustrating the display substrate in FIG. 7. FIG.10 is a cross-sectional view illustrating the method for manufacturingthe display substrate shown in FIG. 9.

Referring to FIGS. 9 and 10, a display substrate 202 according to thepresent embodiment may include a gate line GL, a data line DL, aswitching transistor Qs, a light-blocking pattern 250, a color layer260, and a pixel electrode PE. Each pixel area Px may include theswitching transistor Qs, the color layer 260, and a storage capacitorCst.

The gate line GL may extend in a first direction of the displaysubstrate 202. The data line DL may extend in a second directiondifferent from the first direction and cross the gate line GL. The gateline GL and the data line DL may be connected to the switchingtransistor Qs. The switching transistor Qs may include a first gateelectrode GE1 connected to the gate line GL, a first source electrodeSE1 connected to the data line DL1, and a first drain electrode DE1spaced apart from the first source electrode SE1.

The light-blocking pattern 250 may be formed in a region of the basesubstrate 210 corresponding to the gate line GL, the data line DL, andthe switching transistor Qs.

The color layer 260 may be formed on a second insulting layer 230 formedon the base substrate 210 on which the first source and drain electrodesSE1 and DE1 are formed. The color layer 260 may include a plurality ofnanoparticles. For example, the nanoparticles may include gold (Au),silver (Ag), platinum (Pt), palladium (Pd), cobalt (Co), copper (Cu),molybdenum (Mo), indium phosphide (InP), cadmium selenide (CdSe), copperindium selenide (CuInSe₂), copper indium sulfide (CuInS₂), gold indiumsulfide (AgInS₂), indium phosphide/zinc sulfide (InP/ZnS), etc. Eachcolor of the color layer 260 formed in the pixel areas Px may bedifferent from each other. The color layer 260 having the differentcolors may depend on the size of the nanoparticle or the kind oftransition metal of the nanoparticle.

The pixel electrode PE may be electrically connected to the switchingtransistor Qs. The pixel electrode PE may be formed on the basesubstrate 210 on which the color layer 260 having the nanoparticles isformed.

Referring to FIG. 10, a method for manufacturing the display substrate202 according to the present embodiment will be explained as follows.The switching transistor Qs and the light-blocking pattern 250 may besequentially formed on the base substrate 210. A nanoparticle formed inPEG may be dropped on the base substrate 210 including the transistor Qsand the light-blocking pattern 250 to form the color layer 260. Formingthe nanoparticle according to the present embodiment is substantiallythe same as the method for manufacturing the nanoparticle according tothe previous embodiment described in reference to FIG. 1. Using thenanoparticle formed in PEG to manufacture the color layer 260, thecharacteristics of the nanoparticle having high color reproducibilitymay be maintained and costs for manufacturing the nanoparticle may bedecreased.

Then, the pixel electrode PE may be formed on the base substrate 210including the color layer 260 to manufacture the display substrate 202.

Although not shown in the figures, the color layer including thenanoparticle may be formed on another substrate that covers the basesubstrate 210, which includes the switching transistor Qs and the pixelelectrode PE, and may be formed in the pixel area facing the pixelelectrode to manufacture a display substrate.

The present invention allows a nanoparticle to be formed using PEG as asolvent. PEG is cheap and less toxic, and PEG used in forming thenanoparticle may be recycled. A method for manufacturing thenanoparticle may be used in a method for manufacturing a light-emittingelement, a method for manufacturing a display substrate, etc., and thusthe productivity of the light-emitting element and the display substratemay be improved.

The foregoing is illustrative of the present invention and is not to beconstrued as limiting thereof. Although a few embodiments of the presentinvention have been described, those skilled in the art will readilyappreciate that many modifications are possible in the embodimentswithout materially departing from the novel teachings and advantages ofthe present invention. Accordingly, all such modifications are intendedto be included within the scope of the present invention as defined inthe claims. For example, while only transition metal complex isexplicitly disclosed as the precursor in the interest of clarity ofdescription, other substances known to be suitable for nanoparticleproduction and miscible with PEG is contemplated. Therefore, it is to beunderstood that the foregoing is illustrative of the present inventionand is not to be construed as limited to the specific embodimentsdisclosed, and that modifications to the disclosed embodiments, as wellas other embodiments, are intended to be included within the scope ofthe appended claims.

1. A method for manufacturing a nanoparticle, the method comprising:mixing a precursor with polyethylene glycol (PEG) to form a firstmixture; and thermally decomposing the first mixture.
 2. The method ofclaim 1, wherein PEG has a weight average molecular weight in a range ofabout 1,500 to about 4,000.
 3. The method of claim 1, wherein the firstmixture is thermally decomposed by agitation at a temperature in a rangeof about 100° C. to about 300° C.
 4. The method of claim 1, furthercomprising: mixing the PEG, after thermal decomposition, with ahydrophobic solution having a higher hydrophobicity than the PEG; andseparating solid-state PEG from the nanoparticle, the solid-state PEGprecipitating out of the hydrophobic solution.
 5. The method of claim 4,wherein the first mixture is collected via transforming a phase ofsolid-state PEG.
 6. The method of claim 4, wherein the hydrophobicsolution comprises one of hexane, chloroform, and cyclohexane.
 7. Themethod of claim 1, wherein the precursor comprises a first transitionmetal complex including a first transition metal that forms a core ofthe nanoparticle.
 8. The method of claim 7, wherein the nanoparticlecomprises one of indium phosphide (InP) and cadmium selenide (CdSe). 9.The method of claim 7, further comprising forming an outer layer on thenanoparticle using a second transition metal complex, wherein formingthe outer layer comprises: mixing the second transition metal complexwith the first mixture after thermal decomposition to form a secondmixture; and thermally decomposing the second mixture.
 10. The method ofclaim 9, further comprising: mixing the thermally decomposed secondmixture including the nanoparticle with the outer layer with ahydrophobic solution having a higher hydrophobicity than the PEG; andseparating solid-state PEG from the nanoparticle with the outer layer byprecipitating the solid-state PEG in the hydrophobic solution.
 11. Themethod of claim 10, wherein the first mixture is collected viatransforming a phase of solid-state PEG.
 12. The method of claim 9,wherein the outer layer comprises zinc sulfide (ZnS).
 13. The method ofclaim 1, wherein the nanoparticle comprises at least one of transitionmetal oxide, transition metal sulfide, transition metal selenide,transition metal telluride, transition metal nitride, transition metalphosphide, and transition metal arsenide.
 14. The method of claim 13,wherein the transition metal comprises at least one of zinc (Zn),cadmium (Cd), mercury (Hg), gallium (Ga), indium (In), tin (Sn), lead(Pb), and copper (Cu).
 15. A method for manufacturing a light-emittingelement, the method comprising: thermally decomposing a first mixtureincluding a precursor mixed with PEG to form a nanoparticle; forming afirst electrode layer on a substrate; forming a light-emitting layerhaving the nanoparticle on the first electrode layer; and forming asecond electrode layer on the light-emitting layer.
 16. The method ofclaim 15, further comprising: mixing the PEG and the nanoparticle with ahydrophobic solution having a higher hydrophobicity than PEG; andseparating solid-state PEG from the nanoparticle, solid-statepolyethylene precipitating from the hydrophobic solution.
 17. The methodof claim 16, wherein the first mixture is collected via transforming aphase of solid-state PEG.
 18. A method for manufacturing a displaysubstrate, the method comprising: thermally decomposing a first mixtureincluding a precursor mixed with PEG to form a nanoparticle; and forminga color layer disposing the nanoparticle in a pixel area of a substrate.19. The method of claim 18, further comprising: mixing PEG and thenanoparticle with a hydrophobic solution having a higher hydrophobicitythan PEG; and separating solid-state PEG from the nanoparticle,solid-state polyethylene being precipitated in the hydrophobic solution.20. The method of claim 19, wherein the first mixture is collected viatransforming the phase of solid-state PEG.